Uterine Fibroids - Symptoms and Causes

Overview

Uterine fibroids are noncancerous growths that develop in the uterus, typically during reproductive years. These growths, called leiomyomas or myomas, rarely become cancerous and do not raise the risk of other uterine cancers.

Fibroids can vary significantly in both quantity and size. Some women may have a single growth, while others develop multiple fibroids. Their size ranges from tiny, microscopic growths to large masses comparable to a grapefruit or larger.

Large fibroids can distort the uterus and may even fill the pelvic or abdominal area, resembling pregnancy.

Common characteristics of fibroids:

Noncancerous uterine growths
Typically appears during reproductive years
Vary in number (single or multiple)
Range from microscopic to very large

Many women have fibroids at some point in their lives without realizing it, as these growths often cause no symptoms. In many cases, fibroids are discovered incidentally during routine pelvic examinations or ultrasounds performed for pregnancy or other reasons.

Signs and Symptoms

Uterine fibroids often cause no symptoms at all. When symptoms do appear, they vary based on the size, number, and location of the fibroids in the uterus.

Common symptoms include:

Heavy or prolonged menstrual bleeding
Menstrual pain or cramping
Periods that last longer than normal
Pelvic discomfort or feelings of pressure
Needing to urinate often
Difficulty emptying the bladder completely
Expanding waistline or bloating
Bowel problems, especially constipation
Discomfort during sex
Pain in the abdomen or lower back

In rare cases, a fibroid might cause sudden, intense pain if it outgrows its blood supply and begins to die.

Fibroids are typically classified by where they grow:

Intramural: within the uterine wall.
Submucosal: bulging into the uterine cavity.
Subserosal: on the outer surface of the uterus.

When to Seek Medical Care

Contact your healthcare provider if you experience:

Ongoing pelvic pain
Heavy periods that interfere with daily life
Bleeding between periods
Problems emptying your bladder
Constant fatigue (which may signal anemia from blood loss)

Seek immediate medical attention if you have severe vaginal bleeding or sudden, sharp pelvic pain.

What Causes Uterine Fibroids?

Scientists aren’t completely sure why uterine fibroids form. Several factors likely work together to cause these growths.

Genetic Factors

Changes in genes appear to play a key role in fibroid development. Research shows that fibroid cells often contain different genetic patterns than normal uterine muscle cells.

Hormonal Influence

Hormones, especially estrogen and progesterone, strongly affect fibroid growth:

Fibroid cells have more hormone receptors than normal uterine cells
These hormones help fibroids grow larger
Fibroids typically shrink after menopause when hormone levels drop

Growth Factors

Proteins that regulate cell growth, such as insulin-like growth factor, may encourage fibroids to develop and expand.

Cellular “Glue”

The material between cells (extracellular matrix or ECM) is more abundant in fibroids, giving them their firm texture. This substance:

Holds cells together
Stores growth-promoting compounds
Changes how fibroid cells function

Development Process

Fibroids likely begin from a single stem cell in the uterine muscle. This cell multiplies repeatedly until it forms a distinct mass separate from surrounding tissue.

Fibroids grow in different ways:

Some grow quickly
Others grow slowly
Some maintain the same size
Some experience growth spurts
Some shrink without treatment

Pregnancy can affect fibroids in interesting ways. Some fibroids that form during pregnancy disappear afterward as the uterus returns to its normal size.

Risk Factors

Several factors may increase the chance of developing uterine fibroids. While these growths can affect anyone of reproductive age who was born female, certain groups face higher risks:

Race and Ethnicity

Black people tend to develop fibroids more frequently
They often get fibroids at younger ages
Their fibroids may be larger, with more severe symptoms

Genetic Factors

Having a mother or sister with fibroids increases your risk

Lifestyle and Health Factors

Early onset of menstruation (before age 10)
Obesity
Vitamin D deficiency
Diet high in red meat
Diet low in green vegetables, fruit, and dairy products
Alcohol consumption, including beer

Many people with multiple risk factors never develop the disease, while others with no known risk factors do.

Possible Complications

Fibroids During Pregnancy

Uterine fibroids are typically not dangerous, but they can sometimes lead to problems. Many women with fibroids get pregnant without issues. Submucosal fibroids, which grow into the uterine cavity, can hinder pregnancy and raise the risk of miscarriage.

Women with fibroids who do become pregnant may face higher risks of certain complications, including:

Placental abruption: This serious condition occurs when the placenta separates from the uterine wall before delivery.
Poor fetal growth: The baby might not develop at the expected rate during pregnancy.
Early delivery: Babies may be born before the 37th week of pregnancy.

Heavy menstrual bleeding from fibroids can lead to anemia, a condition where you don’t have enough red blood cells. Your doctor might recommend iron supplements to prevent or treat anemia. In severe cases, blood transfusions may be necessary.

Ways to Reduce Risk

While it may not be possible to completely prevent uterine fibroids, most don’t require treatment.

Healthy lifestyle choices might help lower your risk:

Maintain a healthy weight
Exercise regularly
Eat a balanced diet rich in fruits and vegetables

Some studies suggest that hormonal birth control methods may affect fibroid risk:

Birth Control Type	Potential Effect on Fibroid Risk
Birth control pills (when used by an adult)	May reduce risk
Long-acting progestin contraceptives	May reduce risk
Birth control pills before age 16	May increase risk

Researchers continue to investigate other potential prevention strategies.